Ionic Compounds &
Covalent Bonding
Forming Chemical Bonds
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Chemical Bond: the force that holds atoms together.
 May form by the attraction between a positive nucleus and
negative electrons, which result in positive and negative ions.
 This is because of valence electrons, which are the electrons in
the outer shell of the electron cloud that are involved in bonding.
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Group 1: 1 valence electron
Group 2: 2 valence electrons
Group 13: 3 valence electrons
Group 14: 4 valence electrons
Group 15: 5 valence electrons
Group 16: 6 valence electrons
Group 17: 7 valence electrons
Group 18: 8 valence electrons (maximum amount allowed)
Formation of Ions
Ion: an atom with a charge (gain or loss of electrons).
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Cation – positive ion (lost electrons)
Anion – negative ion (gained electrons)
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Atoms gain or lose valence electrons to obtain a
complete outer energy shell.
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1.
2.
3.
4.
5.
6.
(lose to get to 0 / gain to get to 8)
Group 1: +1
Group 2: +2
Group 13: +3
Group 15: -3
Group 16: -2
Group 17: -1
(loses its 1 valence electron to have zero)
(loses its 2 valence electrons to have zero)
(loses its 3 valance electrons to have zero)
(gains 3 valence electrons to have eight)
(gains 2 valence electrons to have eight)
(gains 1 valence electron to have eight)
Ionic Compounds Contain Ions
(basically you are adding positives and negatives
and balancing to equal 0)
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Net charge of a compound must be ZERO.
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Total positive charge = Total negative charge
If the positive ion does not equal negative ion,
*subscripts* are used to help balance total charges.
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Symbols, Charges, Switch and Reduce.
Example: Sodium, Na, group 1, will lose 1 valence
electron (electrons are negative, gives it a +1 charge)
Chlorine is group 17, will gain 1 more electron to get to
18 and be like a noble gas, giving it -1 charge (gains 1
negative electron).
Together, +1 and -1 are 0, so the compound for Sodium
and chlorine is NaCl, named Sodium chloride.
More examples of ionic compounds
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A compound with Calcium and chlorine forms
like this:
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Calcium is group 2, so loses 2 electrons, +2
charge
Chlorine, group 17, gains 1 electron, -1 charge.
Symbols: Ca+2 Cl-1 Symbols, charges, switch,
reduce (by switch, we mean switch the charges to
the opposite atom, make it a subscript, drop the
charge)
Ca+2 Cl-1
So the formula is Ca1Cl2.
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There should be 2 Chlorines with 1 Calcium to make
this compound neutral. You can drop the ‘1’ as a
subscript. CaCl2 Calcium chloride
Properties of Ionic Compounds
and hints for naming/writing:
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Ionic Compounds (Ionic Bonding):
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Bonding between positive & negative ions.
The *metal (groups 1,2, Al and B in 13, and the transition
metals) will LOSE ELECTRONS TO BECOME POSITIVE.
The *nonmetals (groups 15, 16, 17) will GAIN ELECTRONS
TO BECOME NEGATIVE (group 14 shares)
Positive ions transfer their electrons to negative ions.
Between a metal cation and a non-metal anion.
Most called salts, or oxides if the non-metal is oxygen.
Strong attractive forces that result in crystal lattice
structures.
High melting points, high boiling points, hard-rigid-brittle
solids.
Binary Compounds with
Polyatomic ions
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Compounds containing more than 2 elements
Polyatomic ions (PAI)
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These are groups of atoms covalently bonded but
have one charge, and as a group behave as one
substance, example: sulfate ion is SO4-2. In this PAI,
there is one Sulfur, 4 Oxygens, together they have a
charge of -2.
If you remember from your Lewis structures and studies of
valence electrons, this means there are 2 extra electrons
in the bonding process.
Binary with Polyatomic Ions, cont’d
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The PAI acts as one unit, and then can bond
with a metal or oppositely charged ion to form
an ionic bond.
The bonding between the atoms IN the PAI is
covalent, the bonding between the PAI
(polyatomic ion) is *ionic
Example: Sodium sulfate, a product found in
soaps and shampoos, is Na2SO4
You have a chart with polyatomic ions, *learn
it!
Types of Compounds
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Covalent Compounds (Covalent Bonding)
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Bonding in which valence electrons are shared.
Between only non-metals
A molecule is formed when two or more atoms bond
covalently.
 Most elements when found uncombined in nature are
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monatomic, which means there is one individual atom.
A few exceptions include atoms that must exist
diatomically, these molecules contain 2 atoms.
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These are bound covalently, and include:
Hydrogen H2
Oxygen O2
Chlorine Cl2
Iodine I2
Nitrogen N2
Fluorine F2
Bromine Br2
Metallic Bonding
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Transition metals, groups 3-12, or the d block, form
metallic bonds with each other, which are strong lattice
structures where the positive nuclei are rigid and the
electrons travel in the spaces between:
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They do not share valence electrons with neighboring
atoms nor do they lose electrons to form ions when
bonding with other transition metals.
The outer energy levels of the metals atoms overlap.
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Electron Sea Model: all metal atoms in a metallic
solid contribute their valence electrons to a sea of
electrons (called delocalized electrons- because
they are free to move and form a metal cation).
Metallic Bond: the attraction of a metallic cation for
delocalized electrons.
Metallic compound properties
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Properties: physical properties of metals can
be explained by metallic bonding.
High Melting Point
High Boiling Point
Malleable
Ductile (they can be drawn into wires)
Durable
Conductors of heat and electricity
Metallic compounds cont’d
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Alloy: a mixture of elements that has metallic
properties.
Alloy’s properties are different than the
individual metals in the alloy.
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Examples include: stainless steel, brass, and
bronze which are all mixtures of different
transition metals